1. Field of the Invention
The present invention relates to a liquid discharge head which is capable of discharging a liquid so as to form great many flying liquid drops, thereby effecting a desired recording operation. The present invention also relates to a method of manufacturing the liquid discharge head and a liquid discharge recording apparatus using the liquid discharge head. In particular, this invention relates to an orifice plate formed with a number of liquid discharge holes (herein after, referred to as orifice holes).
However, in the present invention, the term xe2x80x9crecordingxe2x80x9d is used to mean not only an operation in which an image that is a character or a picture is recorded on a recording medium, but also another kind of operation for recording an image that is a pattern not having a certain specific meaning.
2. Description of the Related Art
In the past, there has been known an ink jet recording apparatus in which a sort of recording liquid (ink) is discharged through a number of orifice holes formed on a liquid discharge head so that a predetermined recording operation may be effected in a desired manner. In particular, such kind of ink jet recording apparatus has been considered to be an excellent recording apparatus since it can perform a recording operation at a high recording speed with only a low noise.
FIG. 14 is an explanatory perspective view which is used to serve as an example indicating a conventional liquid discharge head of the type mentioned in the above. In detail, the liquid discharge head shown in FIG. 14, comprises a substrate plate 1001, a top plate 1002 and an orifice plate 1004. The substrate plate 1001 has a plurality of heating elements 1005 which serve as energy generating elements for generating a necessary amount of energy needed for effecting a desired ink discharge. The top plate 1002 is provided on the upper surface of the substrate plate 1001 and has a plurality of grooves each serving as a liquid flowing path 1006, located in positions corresponding to the heating elements 1005. The orifice plate 1004 is provided in contact with the end faces of both the substrate plate 1001 and the top plate 1002, and has a plurality of ink discharge orifice holes 1012 formed in positions communicated with the above ink flowing paths 1006.
In more detail, the orifice holes 1012 formed on the orifice plate 1004 are extremely small in their sizes. In fact, how these orifice holes 1012 are formed will have an important influence on the discharge characteristic of the liquid discharge head. Namely, as far as the orifice plate 1004 of the liquid discharge head is concerned, since extremely small orifice holes 1012 are to be formed, it is required that the orifice plate 1004 as a whole should have an excellent workability (easy to be shaped into any desired shape). Further, since the orifice plate is in direct contact with the ink, the plate itself is required to have a sufficient ink resistance (not easy to be corroded by the ink).
As a material which can be used to form the orifice plate 1004 and which can satisfy the above requirements, it has been allowed to use a thin metal sheet made of SUS, Ni, Cr or Al. Also, it has been allowed to use one of the following several kinds of resin films whose thickness and properties are easy to achieve at a low cost. In detail, these resin films may be made of polyamide, polysulfone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, or polyproplene.
On the other hand, with the progress and development of the recording technique during recent years, it has been required that the recording operation should be performed at a high speed with a high precision. For this reason, the size (diameter) of each orifice hole is required to be further smaller and the orifice holes are needed to be arranged on the orifice plate with an increased density. In order to meet these requirements, there have been suggested various improved methods for forming the orifice holes. For example, when the orifice plate is made of a resin film, these orifice holes may be formed by virtue of laser treatment which is suitable for forming fine small holes. Further, when a metal is used to manufacture the orifice plate, the orifice holes may be formed with the use of an electrocasting method.
However, when the orifice holes are arranged with an increased density and each of the orifice holes has become smaller, a problem will be that orifice plate having orifice holes formed thereon will be difficult to be combined correctly with the liquid flow paths without forming any gaps. To cope with the above problem, Japanese Patent Laid-Open No. 2-187342 has disclosed an improved method in which an orifice plate made of a resin film is at first combined with a head main body which was previously formed by combining together a substrate plate and a top plate, then a laser treatment is used so as to form orifice holes on the orifice plate. Further, Japanese Patent Laid-Open No. 204048 has suggested another improved method shown in FIG. 15. As shown in the drawing, an orifice plate 1024 made of a resin such as a dry film is at first softened by adding heat. The softened orifice plate 1024 is then pressed on to the combining surface of a head main body 1023 which was previously formed by combining together a substrate plate 1021 and a top plate 1022, so that the orifice plate 1024 may be partially combined with a plurality of liquid flow paths 1026 formed on the head main body. Subsequently, a photolithography technique or a laser treatment is employed to form a desired liquid discharge head having a plurality of orifice holes 1032 located in positions corresponding to the liquid flow paths 1026.
On the other hand, in order to ensure a stabilized direction for ink discharge, the diameter of each orifice hole should be made smaller along its ink discharge direction. Namely, it is preferred that each orifice hole be formed into a taper configuration. However, in the process of forming tapered orifice holes, it is preferred that a plurality of orifice holes are at first formed in the orifice plate, followed by combining the orifice plate on to the head main body. In fact, such kind of orifice plate is so formed that the portions surrounding each orifice hole is projected towards the head main body. In this way, by engaging the projected portions into the liquid flow paths of the head main body, the positioning of the orifice plate on to the head main body may be made easy.
However, there are at least the following problems associated with the above described conventional liquid discharge head.
Namely, in the above discussed method, an orifice plate is made of a resin film such as a dry film, the formed orifice plate is then softened by adding a heat. Subsequently, the softened orifice plate is then pressed on to the combining surface of a head main body, so that the orifice plate may be partially combined into a plurality of liquid flow paths formed in the head main body. In this way, although it is allowed to ensure a desired precision when the plurality of orifice holes are engaged with the liquid flow paths, there had been existing the following problems.
A first problem is that when the softened orifice plate is pressed on to the combining surface of the head main body, it will be difficult to control an amount of the resin invading into the liquid flow paths. Further, if the diameter of each orifice hole is extremely small and these orifice holes are arranged with a high density, an amount of resin invaded into the liquid flow paths will greatly affect the liquid discharge characteristic of the liquid discharge head, undesirably making a liquid discharge amount of one liquid flow path different from that of the other.
Moreover, when a resin film is used to form an orifice plate, the orifice holes are formed by virtue of laser treatment. However, if the laser treatment is conducted after the orifice plate has been combined on to the head main body, some kinds of extraneous materials caused due to ablation in the laser treatment will invade into the liquid flow paths. If such extraneous materials get into the liquid flow paths, the orifice holes will get choked. As a result, these extraneous materials will adhere on to the heating elements, rendering it difficult to discharge ink through these orifice holes. On the other hand, when the orifice plate is so formed that the surrounding portion of each orifice hole is projected towards the head main body, all the projected surrounding portions may be engaged into the liquid flow paths of the liquid discharge head, so that the positioning of the orifice plate on to the head main body may be made easy with a high precision, However, since all the projected portions have to be engaged into the liquid flow paths, it will be difficult to make an easy management on an engagement tolerance between the projected portions and the liquid flow paths. On the other hand, if such engagement tolerance is alleviated, it will be difficult to ensure a necessary precision in positioning the orifice holes with respect to the liquid discharge paths. Moreover, if the engagement tolerance is alleviated, a position of one projected portion engaged with one liquid flow path will be different one from the other. As a result, it will be difficult to manufacture a liquid discharge head whose orifice holes can uniformly discharge liquid without any irregularity.
In view of the above, it is an object of the present invention to provide a liquid discharge head capable of ensuring a precision in positioning orifice holes of an orifice plate with respect to the liquid flow paths, preventing any possible failure liquid discharge which will otherwise be caused by a defect in forming the orifice holes. It is another object of the present invention to provide a method of manufacturing the liquid discharge head and a liquid discharge recording apparatus using the liquid discharge head.
In order to achieve the above objects, the liquid discharge head according to the present invention, is equipped with a plurality of energy generating elements capable of generating energy for use in liquid discharge, including a head main body having a plurality of liquid flow paths arranged in parallel with one another corresponding to the energy generating elements, said liquid flow paths having their openings formed on one end face of the head main body, further including an orifice plate having a plurality of orifice holes communicated with the liquid flow paths, so that the liquid discharge head is capable of performing a recording operation on a recording medium by discharging liquid through the orifice holes, characterized in that:
the head main body has a plurality of dummy liquid flow paths which will not be used in a recording operation but are provided on either side of the plurality of the liquid flow paths and are arranged in parallel with these liquid flow paths, while the orifice plate has, on its combining surface for combining with the head main body and in positions corresponding to the dummy liquid flow paths, a plurality of projected portions capable of engaging with open ends of the dummy liquid flow paths.
The liquid discharge head of the present invention formed in the above manner, has a plurality of dummy liquid flow paths which will not be used in a recording operation but are provided on either side of the plurality of the liquid flow paths, while the orifice plate has, on its combining surface with the head main body and in positions corresponding to the dummy liquid flow paths, a plurality of projected portions capable of engaging with open ends of the dummy liquid flow paths. Therefore, when the orifice plate is to be combined with the head main body, it is allowed to easily effect the positioning of the orifice holes with respect to the liquid flow paths, simply by engaging the projected portions of the orifice plate with the dummy liquid flow paths.
Further, there is also provided a method of manufacturing a liquid discharge head of the present invention, which is equipped with a plurality of energy generating elements capable of generating energy for use in liquid discharge, includes a head main body having a plurality of liquid flow paths arranged in parallel with one another corresponding to the energy generating elements, the liquid flow paths having their openings formed on one end face of the head main body, further includes an orifice plate having a plurality of orifice holes communicated with the liquid flow paths, so that the liquid discharge head is capable of performing a recording operation on a recording medium by discharging liquid through the orifice holes, characterized in that the method comprises the steps of:
forming a plurality of dummy liquid flow paths which are provided on either side of the plurality of the liquid flow paths and in parallel with these liquid flow paths;
forming a plurality of projected portions capable of engaging with open ends of the dummy liquid flow paths, with the projected portions located in positions corresponding to the dummy liquid flow paths and formed on the orifice plate""s combining surface for being combined with the head main body;
combining the orifice plate with the head main body after the projected portions are combined with the open ends of the dummy liquid flow paths for effecting the positioning of the liquid flow paths with respect to the orifice holes.
With the use of the method for manufacturing a liquid discharge head of the present invention, since it is allowed to form the dummy liquid flow paths in the same process for forming the liquid flow paths (capable of discharging liquid) in the head main body, it has become possible to manufacture a liquid discharge head having a high positioning precision, without a necessity of increasing production steps.
Moreover, even when each projected portion is formed with a dummy orifice hole which does not discharge liquid during recording operation, since it is allowed to form the dummy liquid flow paths in the same process for forming the liquid flow paths (capable of discharging liquid) in the head main body, it is not necessary to have additional production steps for forming the dummy orifice holes.
In addition, when a laser light is used to form orifice holes and to form dummy orifice holes (not for discharging liquid during a recording operation) in the projected portions, the orifice holes and the dummy orifice holes are all formed into tapered configurations. Although these tapered holes have the same angles, the diameters of the liquid discharge openings of the dummy orifice holes will become smaller than those of the liquid discharge openings of the orifice holes, at an extent corresponding to the thickness of the projected portions. For this reason, it is allowed to easily distinguish the orifice holes from the dummy orifice holes, thereby rendering it easy to effect the positioning of the projected portions with respect to the dummy liquid flow paths.